The effects of pyrethroid insecticide deltamethrin on oxidative stress parameters in different tissues of green toad (Bufotes viridis)

Abstract

One of the main causes of declining frog populations is the increased use of pesticides. The toxicity mechanisms for most pesticides in non-target organisms are associated with oxidative stress. The present doctoral thesis examines acute and chronic Bufotes viridis exposure to pyrethroid insecticide deltamethrin (DM). In the part of experiment that examined acute exposure to DM oral application (96 h) was used, while chronic exposure (7, 14 and 21 days) included oral, dermal and combined oral-dermal application. The following oxidative stress, biotransformation and neurotoxicity parameters were analyzed: the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST); the concentrations of glutathione (GSH), sulfhydryl groups (-SH) and thiobarbituric reactive substances (TBARS); the activity of neurotoxicity biomarker-cholinesterase (ChE) and the expression of phase I biotransformation enzyme cytochrome P4501A (CYP1A). The effects of DM were examined on the liver, muscle, gastrointestinal tissue and skin of adult individuals. The obtained results suggest that DM (although it does not tend to accumulate in tissues) can be hazardous to amphibians and that pesticide exposure modulates the parameters of oxidative stress in selected toad tissues. The data show that the DM-induced systemic toxicity was dose-, route of application- and time-dependent. Toads exposed to this insecticide respond by producing tissue-specific adaptive responses in the course of establishing cell defense to the resulting oxidative stress. The present investigation supports the hypothesis that oxidative stress is one of the steps of pesticide-induced toxicity and that further examination are required to elucidate the entire mechanism.

Jedan od glavnih uzroka opadanja populacije žaba u svetu je povećana upotreba pesticida. Mehanizmi toksičnosti za većinu pesticida u non-target organizmima su povezani sa oksidativnim stresom. U ovoj doktorskoj disertaciji ispitivan je efekat akutne i hronične izloženosti zelene krastave žabe Bufotes viridis piretroidnom pesticidu deltametrinu (DM). U delu eksperimenta koji se bavio akutnim izlaganjem DM (96 h), primenjen je oralni način aplikacije, dok je hronično izlaganje (7, 14 i 21 dan) uključivalo oralnu, dermalnu i kombinovanu oralno-dermalnu aplikaciju. Analizirani su sledeći parametri oksidativnog stresa, biotransformacije i neurotoksičnosti: aktivnosti superoksid dismutaze (SOD), katalaze (CAT), glutation-peroksidaze (GSH-Px), glutation-reduktaze (GR) i glutation-S-transferaze (GST); koncentracije glutationa (GSH), sulfhidrilnih grupa (-SH) i tiobarbiturnih reaktivnih supstanci (TBARS); aktivnost biomarkera neurotoksičnosti-holinesteraze (ChE) i ekspresija biotransformacionog enzima faze I-citohroma P4501A (CIP1A). Efekti DM ispitivani su na jetri, mišiću, gastrointestinalnom tkivu i koži adultnih jedinki. Rezultati ove doktorske disertacije sugerišu da deltametrin (iako nema tendenciju akumuliranja u tkivima) može biti opasan za vodozemce i da izloženost pesticidima modulira ispitivane parametre oksidativnog stresa u tkivima zelenih krastavih žaba. Dobijeni podaci pokazuju da je sistemska toksičnost izazvana deltametrinom zavisila od doze, načina i vremena aplikacije pesticida. Jedinke izložene ovom insekticidu su stvorile specifične adaptivne reakcije tkiva u cilju odbrane ćelija od rezultirajućeg oksidativnog stresa. Sadašnje istraživanje podržava hipotezu da je nastanak oksidativnog stresa jedan od razloga toksičnosti pesticida, ali potrebno je dalje ispitivanje da bi se ceo mehanizam u potpunosti rasvetlio.